This invention relates to wellhead systems and is specifically directed to seal assemblies, often referred to as pack-off assemblies, for sealing the annular space, often referred to as an annulus or gland, between a wellhead casing hanger and the surrounding cylindrical wall of a wellhead.
The U.S. Pat. No. 3,468,558 which issued as early as 1969, and later patents such as U.S. Pat. No. 3,871,449 explain the operation and purpose of pack-off assemblies as well as the various ways of running and setting the pack-off, i.e., sealing the annulus.
These patents also show different types of pack-offs for these pack-off assemblies and U.S. Pat. Nos. 3,797,864 of Hines and Ortolon and 4,521,040 of Slyker and Pettit illustrate more recent pack-offs which comprise an elastomeric ring interposed between two metallic seal rings with each metallic seal ring having a pair of lips extending toward the elastomeric material. Upon compression of the elastomeric material, the lips are forced outwardly towards the surrounding walls to thus seal the annulus with both the elastomeric material and metal.
It is an object of this invention to improve such prior art pack-off assemblies by providing such pack-off assemblies with better sealing capabilities, more accommodation to misalignment, minimum travel of the pack-off during setting, and ease of retrieval of the pack-off. Other advantages of this invention will be mentioned after the Summary, infra.